Pentagon worries, page-9

The reason that the Attack class will be powered by lead acid is because the Naval Group still hasn't produced a working Li-ion powered boat. If we have gone for the Japanese proposal, we would have gotten something with Li-ion battery as part of the power train. Having said that, the Japanese consortium was hopeless in commercial maneuvering when compared with the Naval Group (it was the first time a Japanese consortium to be involved in a major arms export bid).